Twitter said the news of Sir Alex Ferguson’s retirement received more than 1.4 million mentions in the first hour after the story broke at 9.18am.

It compares with one million mentions in the four hours after the death of Lady Thatcher was first announced last month.

The original tweet from Manchester United was retweeted or made a favourite tweet more than 18,000 times, while the official club hashtag £ThankYouSirAlex had more than 100,000 mentions within the hour.

Dozens of stars took to Twitter and Facebook to pay tribute.

David Beckham said: “I’ve just seen the news on Sir Alex.

"As I have said many times before the boss wasn’t just the greatest and best manager I ever played under he was also a father figure to me from the moment I arrived at the club at the age of 11 until the day I left.

“Without him I would never have achieved what I have done in my career.

"He understood how important it was to play for your country and he knew how much it meant to me.

“After ‘98 without the manager I would have found it virtually impossible to cope with the attention I was getting on and off the field and for this I will always be grateful to him for his support and protection.

“I am truly honoured to have been guided by the greatest manager in football and to have had the career that I had under him.

“Thank you boss and enjoy the rest!”

Within an hour this statement had been “liked” by more than 95,000 people.

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Former Man Utd player Michael Owen helped lead the way with questions on who will succeed English football’s most successful boss.

Owen tweeted: “What an act to follow. I guess only Mourinho would have the confidence to strut through the door. If it were me, I’d go for Moyes.

“I was adamant he’d do another year or two. Delighted that he has gone on his terms. Lifting the Trophy next week will be the perfect ending.”

Former United keeper Peter Schmeichel tweeted: Disappointed, shocked, sad. Didn’t think THAT day would be today."

Eamonn Holmes said simply: “We will never see his like again. He is an extraordinary man.”

Other who paid tribute were former player Cristiano Ronaldo and London 2012 Olympic double gold medallist Usain Bolt.

Simply Red frontman and Manchester United fan Mick Hucknall tweeted: "So, the end of an era. Sir Alex Ferguson was, and will remain MAGNIFICENT!! The greatest football manager in the history of the game."

Meanwhile, TV presenter and Manchester United supporter Angus Deayton spoke of Ferguson’s sheer skill - on and off the pitch.

“It’s a hard act to follow. He is the sort of person who could have succeeded in any career.”

And a fellow Man Utd fan, Lord of the Rings star Dominic Monaghan, appeared in shock at the departure.